Merge branch 'es/local-atomic-push-failure-with-http' into maint

Merge branch 'es/local-atomic-push-failure-with-http' into maint

"git push --atomic" that goes over the transport-helper (namely,
the smart http transport) failed to prevent refs to be pushed when
it can locally tell that one of the ref update will fail without
having to consult the other end, which has been corrected.

* es/local-atomic-push-failure-with-http:
  transport-helper: avoid var decl in for () loop control
  transport-helper: enforce atomic in push_refs_with_push